Donald Trump and Hillary Clinton are awaiting the verdict of US voters as one as one of the most divisive and bitterly fought elections in modern American history reached its climax.

Tens of millions of voters across the United States cast their ballots to choose their next president, with long queues reported at polling stations pointing to a high turnout.

Republican Mr Trump was booed as he arrived to vote at a school in Manhattan, accompanied by his wife Melania and daughter Ivanka.

His Democratic rival Hillary Clinton had earlier voted in her home town of Chappaqua, New York, along with her husband Bill.

Mr Trump, who has claimed the election is "rigged" during his campaign, refused to declare if he would concede defeat if he loses on election day.

When asked in an interview with Fox News if he would accept the election result, he replied. "We're going to see how things play out."

Mr Trump's campaign filed a lawsuit in Nevada alleging polling place "anomalies" during early voting in the Las Vegas area.

The lawsuit asked that records from four polling places which stayed open past closing time Friday be impounded and preserved.

But judge Gloria Sturman rejected the request, citing concerns about revealing the identities of poll workers.

Long lines at a Mexican market and several shopping centres prompted the extended hours.

Equipment failures caused delays at some polling stations on election day, while almost 45 million people had already cast early ballots.

The two presidential hopefuls are preparing to spend election night in New York, staging events barely more than a mile apart from each other.

Mrs Clinton will address supporters at the Javits Centre in Manhattan, while Mr Trump has billed his speech at the Hilton Midtown hotel as a "victory party".

There was a heavy police presence in New York after US authorities received intelligence of a possible pre-election al Qaida attack.

Security was heightened at Trump Tower on Fifth Avenue by parking trucks filled with sand outside the building.

More than 5,000 police officers were deployed across New York City to keep order on election night.

Mrs Clinton is aiming to become the first female president in US history, while Mr Trump hopes his pledge to Make America Great Again will win over voters in key swing states.

Victory for Mrs Clinton would see her follow husband Bill into the White House, with the former president becoming the first gentleman - or "first laddie", as some have suggested.

Mr Trump, who has been dogged by allegations of misogyny and sexual misconduct, has targeted battleground states in an effort to get the 270 electoral college votes he needs to become one of the most unlikely victors of a presidential race.

An early exit poll showed some 62% of voters decided before September which candidate they would back, according to CNN.

Only 12% decided over the past week - suggesting that recent revelations about the FBI's investigation into Mrs Clinton's emails and Mr Trump's lewd comments about women and accusations of inappropriate sexual behaviour did not have much impact on Americans as they went to the polls, the broadcaster said.

The CNN exit poll results suggested neither candidate was particularly popular. Only 42% said they "strongly favoured" the candidate they voted for.